


Unauthorized Modifications

by bouquetofwhoopsiedaisies



Series: That Ultra-Kind of Love You Never Walk Away From [4]
Category: Voltron: Legendary Defender
Genre: Alien Biology, Asexual Pidge | Katie Holt, Begging, Half plot half porn, I did not know that was a tag but wow lmao that is perfect, Light Bondage, M/M, Mentions of Masturbation, Multiple Orgasms, Overstimulation, Power Exchange, Probably Inaccurate Science, Sheath Play, Shiro (Voltron)'s Arm as a Vibrator, This is absolutely filthy, Vibrators, With a twist!, a dash of dirty talk and praise kink, as in alien biology, both of these boys are switches who are we kidding they just like to have fun, everyone is over 18 just making that clear, frank discussion of sexual content, slight D/s, smut in chapter 2, yes asexual characters can masturbate if they want to get over it
Language: English
Status: Completed
Published: 2018-09-05
Updated: 2018-09-05
Packaged: 2019-07-07 07:30:25
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 5,276
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/15903702
Author URL: https://archiveofourown.org/users/bouquetofwhoopsiedaisies/pseuds/bouquetofwhoopsiedaisies
Summary: Pidge sighed and slumped in her chair, tossing the dildo back onto the desk.  She grabbed a screwdriver from the top of the desk and adjusted the base.  “Please don’t tell the others about this.  Especially Lance.  I don’t think I could handle th--”“I won’t tell anyone.”  Shiro said quickly, the gears already turning in his head.“Oh thank --”“Provided you give me a copy of the modification codes.”“-- fuck.”  Pidge finished belatedly.  She half-turned around in her chair to look at him suspiciously.  “Wait, why do you need mod codes to make Galra-tech vibrate…?”Shiro didn’t say anything, but he could tell when Pidge got it when her eyes went as wide as saucers.“Wait.No, don’t tell me.”  Pidge turned away from him again.  “I don’t want to know.”(Shiro catches Pidge up to something late at night.  Keith pays the price.)





	1. Chapter 1

**Author's Note:**

> The basic premise of this is neither original nor unique (in that that PLENTY of people have written "Shiro's Galra arm can vibrate" fics before me), but I had fun with this _so I'm throwing my contribution on top of the pile anyway!_. Enjoy.
> 
> I’m still mentally getting used to Shiro’s new arm being the disembodied floaty bluetooth arm of season 7… so this features the older Galra-tech arm. ¯\\_(ツ)_/¯ Other than that, the timing of it could be anywhere. Takes place in the Keith/BoM AU, with that AU’s aforementioned Galra biology.

Some nights, sleep didn’t come easily to Shiro.  

He would have blamed it entirely on the Galra and his year being imprisoned by them, but truth be told, he had been known to suffer bouts of insomnia back on Earth, too.  The Galra may have exacerbated the problem as of late, but Shiro was no stranger to sleepless nights. At least now he could walk around a little to take his mind off things.  That had been denied to him in the prisoner cells on the Galra command ship. The movement helped a little, or at least more than staring up at his ceiling did.

Shiro slipped out of bed, taking care not to disturb Keith as he slept next to him.  He smiled fondly at his boyfriend’s peacefully sleeping face, just barely illuminated with the low blue glow from the narrow strip of Altean lighting that ran along the head of the bed.  They didn’t have to keep that light on, but Keith always insisted; he said it was so they didn’t trip or walk into a wall on the way to the bathroom in the middle of the night, but Keith himself usually slept like the dead and nothing short of the castle-ships sirens would wake him up.  Shiro had a feeling Keith insisted to assuage Shiro’s bruised pride at being in his mid-twenties and finding comfort in the small light, letting him know that he was here and safe and not back in his prison cell or the arena.

Whatever the reason, it did make it easier for Shiro to locate and lace up his boots and slip out of the room without a sound.  He set off down the hall and fell into his usual route, half patrolling for any threats and half just trying to settle his mind enough to go back to sleep.  The castle-ship was silent aside from a low, mechanical hum as they flew through space.

A blinking red light punctured the peaceful mood, and Shiro narrowed his eyes as he approached it.  The screen next to the door of Coran’s laboratory and workshop was flashing a message that said “ _unauthorized personnel_ ” but the alarm seemed to have been stopped by the mechanical device stuck to the side of it.  

Shiro frowned at the closed door.  Had someone snuck onto the castle-ship?  And what were they doing in Coran’s lab? Shiro lifted his Galra-tech arm and prepared to activate it, took a deep breath to clear his head, and pressed the sensor to open the door as he dropped into a fighting stance.  

He wasn’t sure what he was expecting to find inside -- a Galra spy rooting around for information?  Anti-coalition rebels? Sendak?? -- but Pidge working at a desk in her pajamas was certainly not it.  Her head whipped around at the sound of the door opening and her eyes widened to match his as they took in each other.  

“ _Shit_ , Shiro!  You scared the crap out of me!”  Pidge put a hand to her chest.

Shiro deactivated his arm and eased out of his defensive posture.  “What are you doing in here? Shouldn’t you be asleep?”

“Shouldn’t you?”  Pidge replied evasively, and Shiro noticed she was quickly shoving things into a bag.  Tools, wires, a memory chip, a…

Shiro’s eyes widened further.  “Is that a dildo?” Really, calling it a ‘dildo’ was a bit generous; it was about as thick as a pencil at the textured tip and probably only a few inches around at the slightly-wider base, the whole thing curved a bit more than a dick would be.  Then again, Shiro guessed it could be based on some other alien’s phallic shape; he was well-aware that they came in a variety of forms.

Pidge froze at his words, a deer caught in the headlights.  

“That’s-- It-- Uh…”  Pidge glanced back at him, ears pink and glare pointed.  “Look, you’ve got Keith -- plus, you know, actual sexual attraction, which I’d imagine helps significantly -- but some of us need… a little help sometimes.”  She frowned and pointed at him sternly. “I’m still ace, by the way.”

“No, no, I get it.”  Shiro held up his hands.  “We’re both adults, Pidge, it’s fine.  I’m just surprised you’re using Coran’s lab to make it.”

“Unfortunately, the tools I need are connected to the desk here.”  Pidge frowned at what looked like high-tech soldering equipment and more types of screwdrivers than Shiro could ever imagine a use for, all of them hanging from the ceiling by blue Altean glowing threads like a cross between a junk shop and an artistic wind chime.  Shiro vaguely remembered Coran explaining it was the best way to ensure he never lost any tools, even though the humans often grumbled about the threads getting tangled. Pidge sighed and leaned back in her chair. “And I didn’t make it. I bought this Galra-tech dildo at a space mall, and I’m just modifying it.”  

“Modifying it?”  Shiro asked. “You’re sure it’s safe, right?”  

“Yeah, I’m just adding a balmera-core to power the motor I put in it.”  Pidge pushed a button, and the whole dildo started to vibrate. Shiro lifted an eyebrow, and a blush spread over Pidge’s cheeks and she quickly shut it off.  “Look, I just want to deal with my sex drive as fast as possible and then get on with my day. Vibration works the fastest. It’s purely an efficiency thing!”  Her words tumbled out quickly, one after another like a rockslide. She always tended to babble when she was nervous or put on the spot.

“Pidge, I get it.  You don’t have to explain.”  Shiro held up a hand and offered her a reassuring smile.  “You can handle your needs any way you like, no matter your sexuality.”  

Pidge sighed and slumped in her chair, tossing the dildo back onto the desk.  She grabbed a screwdriver from the top of the desk and adjusted the base. “Please don’t tell the others about this.  Especially Lance. I don’t think I could handle th--”

“I won’t tell anyone.”  Shiro said quickly, the gears already turning in his head.  

“Oh thank --”

“Provided you give me a copy of the modification codes.”  

“-- fuck.”  Pidge finished belatedly.  She half-turned around in her chair to look at him suspiciously.  “Wait, why do you need mod codes to make Galra-tech vibrate…?”

Shiro didn’t say anything, but he could tell when Pidge got it when her eyes went as wide as saucers.  

“ _Wait_.  No, don’t tell me.”  Pidge turned away from him again.  “I don’t want to know.”

“I mean, Keith isn’t here _all_ the time…” Shiro mused.  

“ _Shiro_ …”  Pidge bristled.

“Sorry.”  Shiro could see how talking about one’s friends’ sex habits could be awkward.  Truth be told, though, he wasn’t thinking of _only_ the times Keith wasn’t around.  

Pidge tapped a few keys, the computer beeped, and she yanked out the memory stick.  “Here. A copy of the modification codes. Be safe, use protection, all that jazz. And let’s never speak of this again.”  

“Thanks, Pidge.”  Shiro took the proffered device, chuckling as she muttered something about _don’t want to know where that robo-hand has been_...  “And don’t worry, this can stay between us.”  

“It fucking better, or I will hack your arm and make it play ABBA anytime you activate it.”  Pidge threatened lowly.

Shiro stared at her in horror.  “You wouldn’t dare…”

“Don’t test me, Shirogane.”  Pidge pointed her screwdriver at him, and from the glint in her eye and the curve of her grin, Shiro honestly couldn’t tell if she was joking or not.  Best not to cross her.

He cleared his throat.  “Well, I’ll be going, I guess.  Make sure you get some sleep tonight.”

“Mm-hm, you too.”  Pidge turned back to her work.  

Shiro hesitated near the door and looked back.  To each their own, he supposed, but that device really wasn’t all that thick...  “I mean, are you sure you don’t want to make that thing a little bigger?”

“ _Shiro I swear to quiznak--_ ”

He wisely left before she could chuck a screwdriver at him.

~~~~~

Hunk and Pidge may have prided themselves on being the team’s engineering duo, and Matt and Commander Holt might have taken care of more of the mechanical side of the Kerberos mission while Shiro had piloted, but Shiro still knew his way around a toolkit and some computer coding.  It had been a requirement to go to space; all members of any Garrison expedition had to be able to make repairs and pilot themselves in a pinch, just in case something happened to their teammates. So it was little trouble for Shiro to understand the modification codes Pidge had given him and make his own adjustments to the Galra-tech inside his arm (really the only challenge was doing it all left-handed).  He couldn’t imagine asking anyone for help with it, anyway; Pidge would probably spontaneously combust in embarrassment, Hunk would ask too many questions, and Coran would probably figure out what he was up to and treat him to a three hour long spiel about safe alien sex, likely with an informational video featuring a weblum. So that just left himself.

 _“Even pilots need to know the mechanical side like the back of their hand, just in case the need arises in space…”_  Somehow, Shiro didn’t think this was quite what Iverson had meant when he said that.  

Closing up the port on the underside of his arm, Shiro set the screwdriver aside and lifted his hand to examine it critically.  Connecting a new set of neural-based transmission paths left him with a headache, but he knew from Hunk doing maintenance on his arm that the feeling would fade soon enough.  The activation was similar to (but separate from, thank goodness) how he turned his arm into a weapon, but the results would be drastically different.

With just a thought, the metal fingers began to vibrate with a low hum.  Huh. Shiro hadn’t expected it to feel good on his end. It was like a steady, soothing pulse against the scarred tissue where the arm connected to his flesh.  This might be useful for relieving aching muscles… He experimentally touched his fingers to his left forearm and noted the low intensity of the vibrations, just enough to tickle.  Another thought, and they amped up. Yet another, and the intensity left goosebumps prickling any flesh he touched and a shiver running down his spine.

Shiro grinned and shut the vibrations down with a thought.  Perfect.


	2. Chapter 2

**Notes for the Chapter:**

> Do not look me in the eyes this is the filthiest goddamn thing I’ve ever written ~~but something tells me it won’t be the last~~

Keith let out a shout as he came for the fifth time that night, throwing his head back against the pillow and arching into Shiro’s hand.  

“Good boy,” Shiro let him grind onto his vibrating fingers to draw out the orgasm.  His other hand smoothed up Keith’s side and his raised arms to where his hands were tied to the headboard.  They had been going for a while, Shiro repeatedly building him up and backing away to let him teeter at the edge of the cliff before finally letting relief crash over him, then barely giving a moment to rest before starting up again.  Keith was sweaty and flushed under him, chest heaving as he panted, and Shiro couldn’t stop being in awe of how gorgeous he looked coming apart at the seams like this. 

Keith whined and his hips twitched away as he tugged weakly on his bonds, and Shiro lowered the vibration to the first setting and withdrew his fingers.  “Think you’ve got another one in you?” He asked, running a gently-vibrating finger around his flushed folds and up to the mound where his cockhead was already poking out.  Shiro had instructed him to keep his cock sheathed, as he knew the pressure tended to draw out the orgasms. And it was fun to watch Keith squirm with the effort. 

Keith sucked in a sharp breath and did his best to shift away from the touch.  “No… I can’t…” Despite his words, his eyes fluttered shut as Shiro stroked around the opening of his sheath, cockhead twitching and trying to slide out.  It was pain-bordering-on-pleasure, or pleasure-bordering-on-pain; he couldn’t tell which, but he wanted more. 

“I think you can.”  Shiro said mildly, his tone no different than someone musing it might rain today.  He placed his thumb over the emerging cock and gently pressed it back into the sheath.  The action ripped a hiss out of Keith and his body curved up defensively, foot scrabbling against the bed as he writhed.  Shiro circled his thumb very slowly, soothing the organ with little pulses of vibration. “I think you can come again, because I’m telling you to.  You’ll come as many times as I say, won’t you, baby?” 

“Fuck…” Keith threw his head back, eyes shut tight.  “I can’t… it’s too much…”

“Then why are you already grinding into my hand, hm?”  Shiro challenged, eyeing the little circles Keith’s hips were pushing onto his fingers.  “You want this. You want to come as many times as I tell you to. You’re just as curious as I am to find out how many times I can get you to come in one night.”  

“Fuck, yes…” Keith huffed.  Shiro wasn’t entirely sure if it was an agreement or just an exclamation.  But Keith’s curiosity had been nearly palpable when he was letting Shiro tie his hands to the headboard earlier, so it agreement was likely.  

Then again, that had been five orgasms ago.  

Shiro turned off the vibrations with a thought, and Keith whimpered and tossed his head to the side.  “No…” He moaned, lifting his hips up.

“But didn’t you say it was too much?”  Shiro feigned. 

“Want… it…” Keith opened his eyes to stare up at him, and Shiro thought he could drown in those molten amethyst depths.  “Please, more…”

“I thought so.”  Shiro slipped two fingers between his folds.  “You’re such a slut for my fingers in you, baby.”  He turned on the vibration again once he was deep inside, and Keith let out a choked sound as the intensity rocketed up to the second level right away.  Shiro thrust his fingers in and out at a slow, lazy pace, every so often pausing deep inside to rub his thumb over Keith’s soaked labia. “I bet I could keep you coming on my fingers all night long.”  Shiro murmured. “Doesn’t that sound fun, baby?” 

Keith grunted something that sounded like a gruff “no”, and there was just a little too much sass in his tone for Shiro’s taste.  He drew his fingers almost all the way out. “No!” Keith clenched down around nothing, the word taking on a very different meaning now.  

Shiro arched an eyebrow and frowned down at him, fingertips resting just at the edge of his hole and vibrations teasing the sensitive skin and dark curls of hair down there.  “‘No’ what? You’re going to have to be more clear, Keith.” 

‘Clear’ was not the word to describe Keith’s head at the moment, Shiro realized as the man under him slumped back against the bed.  He was nearly gone, too lost in the pleasure to offer up much cognizance. But Shiro wanted him completely gone. Not yet, though; he still needed an answer.  

He moved his fingers just marginally, and Keith’s hips twitched.  “No don’t stop. Please, Shiro, don’t stop. I want it.”

“Then you’re going to be good for me?”  Shiro asked. “You’re not going to talk back, except to use your safeword?”  

Keith bobbed his head, and there was enough clarity in his eyes to let Shiro know he meant it.  “Yes. I promise. I’ll be good.” 

“And you’re going to come as many times as I tell you to?”  Shiro circled the tip of his index finger around the edge of Keith’s hole, careful to keep the rest of his fingers curled up to focus the sensation at that one point.  

Keith bit his lip.  “Y-yeah,” his breath shuddered as Shiro eased two fingers back inside him.  

“Good boy.”  Shiro hooked his fingers just the way he knew Keith liked, drawing a gasp out of him.  “Now let’s see if you can make good on that promise. Because I’m going to keep you coming until you beg me to stop.  Maybe even a little more, just to see what you can handle. And then maybe a little past that, just because I can.” With a thought, he turned up the vibrations to full power as he thrust deep and then held it there.

Keith howled and arched his back off the bed, toes curling.  Shiro laid a hand over his abdomen and felt the taut muscles flexing involuntarily as he edged closer and closer.  Keith pushed his hips down into Shiro’s palm to press the fingers inside him deeper, then moments later, his muscles locked tight around Shiro’s hand and he came again with a loud moan.  

“Very good.”  Shiro smiled and turned the vibrations down to mid-level, then the lowest setting after a few moments.  He left his fingers where they were, though, still curled inside him and humming quietly on low. “I knew you had another one in you, baby.  How about one more?” He traced his thumb around the edge of his sheath, feeling the hard cock underneath the soft skin.

Keith whined and his hips shied away from Shiro’s fingers.  “Too much… it hurts…” He gasped, eyes shut tight. 

Shiro leaned down and laid a placating kiss to his cheek as he drew his fingers out.  They were absolutely soaking with slick cum and hot from both the friction of the vibrations and being enveloped in Keith’s tight heat.  He paused to adjust Keith’s legs, spreading them a little wider, before trailing his still-vibrating hand up his pelvis, over his hip, teasing along his ribs, and up to his heaving chest.  “I think you can do at least one more.” Shiro told him, relishing the hitch of Keith’s breath as he thumbed over a nipple. 

“Th-that’s what you said… the last few times…” Keith squirmed like he wasn’t sure whether he wanted to arch into the touch or away.  “How… how many times are you gonna…?” His words petered off into a soft groan as Shiro left his nipples to trace along his collarbone and throat, the vibrations leaving goosebumps growing under a trail of slick.  

“Hm,” Shiro sucked thoughtfully at a spot under his ear.  His lips pulled up into a grin against his skin. “As many times as it takes.”  

Keith’s breath left him in a rush as he laughed softly.  “You bastard…” 

“Is that any way to talk to the man who holds your fate in his hands?”  Shiro asked, reaching down to cup between Keith’s legs again. He smiled at the gasp that earned and sat up to find Keith grinding into the vibrating metal palm.  “Look at you, ready to go again already… and you said you couldn’t come another time…” Shiro teased and lifted his hand enough to trail his fingers up to his sheath, carefully working one finger inside to press against the tip of his cock.  

Keith cried out and squirmed.  “Ah! Still… still hurts…!” He said that, but his hips were still bucking up into the touch.  

Shiro eased up on the pressure, but didn’t let go.  “But it’s nothing you can’t handle, right, baby? Because you’ll take anything I give you.”  He adjusted his angle to avoid the most sensitive parts and coaxed the surrounding skin into sending sharp shocks of pleasure through his boyfriend, occasionally brushing the too-sensitive areas to skirt the line between pain and pleasure.  

In just a few minutes, Keith was no longer shying away from him and instead rocking up to get more.  Soft gasps and broken pleas spilled from his lips whenever Shiro changed the angle or the vibration level.  Shiro massaged his thumb just outside of the sheath, curling his finger just slightly to pinch the swollen skin between vibrating fingers while letting his knuckle rest on the head of his sheathed cock.  

Keith cried out, his chest heaving and one leg hiking up to open him up further.  “Oh fuck! Shiro, please…!”

“Please what?”  Shiro asked, fingers still and unrelenting as the vibrations continued.  

Keith tossed his head back and his adam’s apple bobbed as he swallowed thickly.  “It’s too much… please, I can’t take it anymore…” 

Shiro switched off the vibration, but he kept a single hot metal finger pressed against the tip of his cock inside the sheath.  Keith deflated, though his abdomen remained tense and taut as a wire ready to snap. He panted heavily, eyes closed.

“This… this is abuse.”  Keith muttered, but Shiro could tell he didn’t really mean it.  “You’re abusing the fact Galra can have multiple orgasms.” He was sweaty and flushed and pouting, but the way he pressed against Shiro’s finger told him he was still enjoying it.  He was nearing his limit, though, almost completely unraveled. 

“I wouldn’t say it’s ‘abuse’...” Shiro shifted his finger just slightly, and relished in the way Keith chased him.  “More like ‘utilizing to the full extent’. Besides, you know your safeword.” He drew his finger out slowly.

Keith shuddered at the sensation.  “ _ Fuck _ …” 

Shiro snorted.  “ _ That  _ is not your safeword.”  He turned the vibrations back on and pressed at the base of his sheath.  Half-formed curses and aborted moans and whimpers bubbled out of Keith as he fought to keep from unsheathing his cock.  Shiro continued the torture for only a minute before dropping a kiss to the corner of his parted lips. “Alright, baby, you can let it out.  But don’t come until I tell you, or I’ll leave my fingers in you all night long until the morning wake-up call.” 

Keith whined and nodded weakly.  “Yes, sir.” 

He let his cock slide out of the sheath, flushed so red it was nearly purple, and Shiro circled his fingers to let the vibrations tease at every ridge and vein as the length emerged.  Keith was nearly beside himself by the time it was finished, babbling incoherent pleas and begging Shiro for something he didn’t even know how to articulate.

“Look at your greedy hole, clenching around nothing,” Shiro let his hand wrap loosely around the base of Keith’s cock, vibrating palm pressed to his pelvis, while his heady gaze travelled lower.  Keith choked on a gasp and squirmed under the touch, slick dripping out of him and soaking the sheets underneath. Shiro used his left hand to push Keith’s legs further apart, then shifted so he could kneel between his spread thighs.  “You want something to fill you up, baby? Something to keep you nice and full…”

“Yes,” Keith moaned.  The corded muscles in his stomach twitched and he squirmed as Shiro trailed his vibrating fingers lower, touch maddeningly light.  The vibrations rippled through every one of the dense, dark curls between his legs, sending shocks of pleasure to the nerves of the skin underneath even when Shiro wasn’t touching him directly.  It was torture of the best kind. 

Shiro let his fingers slip through the soaked skin and parted the folds in time to see another gush of slick leak out of the twitching, reddened hole.  “Six times… going on seven if you’re lucky.” He slid two fingers in deep and tapped his thumb against the underside of the base of Keith’s cock, leaning in to breathe warm air over the head of it.  “Think that’s all you have in you? Or can you give me eight?” 

“ _ Ah _ !  Shiro, please… I can’t… I can’t…”  Keith was close, really close. 

“We’ll see.”  Shiro crooked his fingers, threw the vibrations up to full-power, and swiftly took Keith’s cock down his throat as he pressed his thumb into the base of his cock.  

Keith  _ roared _ and came harder than he had that entire night, maybe even harder than he ever had.  His back arched, his toes curled against the bed, his thighs spread wider as his hips thrust up, and his inner walls clamped so tight around Shiro’s fingers he thought he might never get them back.  Shiro swallowed down his cum and hummed around him, as if the poor man needed  _ another  _ source of vibration when he was already so strung out.  Keith whimpered and his hips twitched like he wasn’t sure if he wanted to get away or closer, so Shiro lowered the vibrations with a thought and suckled at his spent cock as it softened and retreated back into its sheath; what had startled him the first time seeing it had quickly turned into one of his favorite aspects to Keith’s half-Galran anatomy.  

“Shiro…” Keith’s voice was raw and broken between hitched breaths.  “It’s too much, it’s too much…” 

Shiro lowered the vibrations yet again and stroked a fingertip along the walls still fluttering with aftershocks.  Keith let him do it, but when it became clear that the pain-pleasure was veering more toward pain and he could tell the word ‘Voltron’ was rising to his lips, Shiro carefully withdrew his fingers amid the shuddering gasp from his partner.  

“Good job, Keith…” Shiro kissed the jut of his pelvic bone where it met his hip.  “You did so good, baby… so good for me…” He lifted his gaze and admired the rapid, deep rise and fall of Keith’s chest as he came down.  Pausing the vibrations for just a minute, Shiro reached up and untied the cloth binding Keith’s hands to the headboard. Keith left them where he laid them, too tired to lower his hands now that they were free.  Shiro trailed his fingers -- still hot and once again humming along at the lowest setting -- down Keith’s raised arms and down his sides, admiring the way he twitched at the sensation. “Can I do one more thing?”  Shiro asked. 

Keith peeled his eyes open and looked down at him almost warily.  “What?” He trusted Shiro implicitly, but there was no way he would survive another round like that. 

Shiro bracketed his knees on either side of Keith’s hips and leaned over him, wrapping still-vibrating fingers around his own cock.  “Can I come on you?” 

Keith’s eyes, still hazy, darkened with lust.  He really liked that idea. “Yeah.”

Shiro flashed him a smile, then turned up the vibrations in his arm and fisted his cock.  He bit back a groan at the sheer intensity of it -- Keith had put up with this for over an  _ hour _ ?? -- and his supporting arm nearly gave out from under him when he rubbed his thumb over the flushed head.  His focus on Keith and his curiosity for the task at hand had helped keep his own orgasm at bay, mind too focused on coaxing every possible thread of pleasure out of his boyfriend to worry about his own need to come simmering on the back burner.  What had simmered before was now a boil, though, and his cock ached so bad it was almost too good. Strangely enough, the vibrations felt stronger and more intense if he  _ didn’t _ move his hand, so although he must look strange kneeling over his boyfriend with his hand just wrapped around his cock and thumb pressing at the slit, Shiro really couldn’t bring himself to care  _ what  _ he looked like, not when it felt this good.  Keith didn’t seem to mind either, darkly glowing eyes watching him headily and a slow smile spreading over his lips while he drank in the sight of Shiro shuddering and gasping above him as he climbed closer and closer to the same precipice he himself had been thrown over.

Shiro had closed his eyes against the too-many too-good too-everything sensations, so he failed to notice Keith reaching for him until a fingertip lightly traced down what was exposed of his cock below his fist, the touch shockingly different from the tight, vibrating grip he had around himself.  Long, slender fingers wrapped around what he couldn’t reach, no doubt able to feel the vibrations through him, and another hand cupped underneath his balls and squeezed gently. 

Shiro came with a low moan that just barely worked itself into a garbled version of Keith’s name.  His orgasm crashed through him hard enough to make him see stars behind his eyes and hear rushing in his ears.  Almost as if he was experiencing it from afar, he felt his release splatter onto the body below him and heard Keith gasp as it hit his stomach, likely still overly sensitive himself.  Shiro rode out the feeling for a second or two, then uncurled his fingers from around himself. 

“Don’t.”  Keith’s voice stalled his movements, and he opened his eyes to see him watching him, intrigue and playfulness and something sharper showing through the exhaustion.  Keith met his eyes. “Keep going.” 

Shiro sucked in a sharp breath at the command, a breath he lost again moments later when he hissed as he curled his fingers around his softening cock.  “ _ Oh _ …” Fuck, that was intense.  The sensation was just barely on this side of pleasurable, skirting the line of painful before blurring it entirely.  “Keith…  _ Keith _ …” Shiro gasped, his hips twitching away involuntarily.  It was  _ too  _ good…

“Just a little bit longer.”  Keith told him, and Shiro let his head drop to his own chest at the smirk in that warm voice.  That’s what that sharp, unnamed emotion had been on his face: revenge. 

Shiro’s softened cock was starting to burn, the feeling a little too painful to be strictly pleasure, and he was on the verge of begging when Keith told him he could stop.  He shut down the vibrations immediately, one last gasp falling from his lips, and his hand shot away from his spent cock like he had been burned, instead planting itself on the bed near Keith’s shoulder to stop him from collapsing on top of his boyfriend like a puppet whose strings had been cut.  

He had just managed to get his breath back when Keith’s voice filtered in through the haze, warm and humored.  “Now imagine that, but seven times.” 

_ Fuck. _

“I honestly don’t know if I should apologize for that or not.”  Shiro chuckled breathlessly. If he had Galra stamina, he could see that being really,  _ really  _ good, but as it was, it was just daunting.  

Keith snorted derisively and reached up to maneuver Shiro down onto the bed beside him.  “Lie down before you collapse and crush me.” 

“You’d be into it, don’t lie.”  Shiro murmured sleepily and drew Keith into his arms.  “We’re gonna have to clean up…” 

“We can wait a few minutes.  Catch our breath.” Keith hummed.  He picked up Shiro’s Galra-tech hand and ran his fingers over it, examining it.  “This is hot.” 

Shiro smiled lazily.  “It was, wasn’t it?” 

“Temperature-wise, you fucked-out dork.”  Keith chuckled and tapped the warm metal of his palm.  “The metal is hot. Is that uncomfortable?”

“Hm, not really,” Shiro rotated his shoulder and considered it.  “It feels a little warm, where the prosthetic connects. But in a good way.  Like getting a hot massage. The ache that’s usually there is gone right now, actually.”  

“Huh.”  Keith kissed his shoulder.  “Perks all around, then. Doesn’t seem to have any downsides.”

Later, when they got distracted from cleaning up and Keith tried to blow Shiro in the shower and Shiro accidentally activated the vibrations strong enough to rattle the glass shower door, thus startling them both so bad they ended up in a wet, slippery tangle of limbs on the tile floor, they did find one downside to the arm’s modifications.  But overall, the arm was declared a big success. 

**Author's Note:**

> BONUS: how the last scene originally played out in my head in a way that made me almost fall off my bike laughing…
> 
> _“Just a little bit longer.” Keith told him, and Shiro let his head drop to his own chest at the smirk in that warm voice. That’s what that sharp, unnamed emotion had been on his face: revenge. “Ten more seconds, Shiro, you can do it.”_
> 
> _**Ten--?!** Shiro bit off a groan and shifted his grip around his throbbing cock, everything in him begging to let go and end the too-intense sensations._
> 
> _“Eight, seven,” he could hear Keith counting, his voice slow and measured and not going nearly as fast as Shiro needed him to. “Six… five…” Was he slowing down?? “Four…” The number came out soft and heavy, and he trailed off into silence._
> 
> _“Keith…” Shiro opened his eyes and found Keith resting back against the pillow, head turned to the side and the long line of his neck exposed as he… **slept?!** Shiro let out a strangled whine, hips bucking as the pleasure sparked too sharp. “ **Keith!** ” He couldn’t just fall asleep and leave Shiro like this! _
> 
> _A miniscule twitch of his brow gave him away, and Shiro bit back a curse. “Keith you little shit I know you’re not asleep, come on let me stop!” He begged. It was too much, just too much…_
> 
> _Keith opened his eyes and flashed him a grin so impish, it was hard to believe he had just been fucked to the verge of exhaustion only a few minutes ago._  
>  ~~~~~
> 
> I kinda liked it and it did make me laugh, but I thought it didn’t flow well with the rest of it so I cut it. I like my sprinklings of humor, but not so much that it’s distracting or steers the story onto a different track. ¯\\_(ツ)_/¯ So enjoy this snippet like a blooper reel on the bonus disk of an old DVD. But I do adore the idea of these two being so in-tune and comfortable with each other that they can have fun and laugh a little when they fuck. Zero to kinky to giggling in 60 seconds is my kinda sheith :3c 
> 
> Also Keith has 100% gotten accidentally turned on from Shiro giving any of their teammates an innocent massage after a hard day of training. Full-on, red-faced, “yeah sorry I _neeD TO L E **AVE--**_ ” level turned on. It happens and Pidge just stares into the camera like she's on the Office, because she is cursed with the knowledge of exactly _why_ , lmao.


End file.
